expression: lazy init bufAllocator in baseBuiltinFunc

[windtalker]

What problem does this PR solve?

Issue Number: ref #65003

Problem Summary:

What changed and how does it work?

bufAllocator is only used in VecEval mode, however, currently, TiDB will always init bufAllocator when construct a baseBuiltinFunc. Although we can assume that almost all the baseBuiltinFunc should support vec evaluation, some code path just does not use VecEval mode, for example:

tidb/pkg/executor/insert_common.go

Line 221 in 7dea15e

row, err = evalRowFunc(ctx, list, i)

For the pure insert workload described in #65003

Before this pr, the heap profile in alloc_objects space

After this pr, the heap profile in alloc_objects space

As it shows, expression.newLocalColumnPool disappears completely, which mean we save 8.32% allocations.

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
  run the workload in planner: optimize the optimizer's CPU and memory usage for INSERT ... ON DUPLICATE KEY UPDATE statements #65003, and all the existing test will cover the code path
• No need to test

  • I checked and no code files have been changed.

Side effects

• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Breaking backward compatibility

Documentation

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features
• Changes MySQL compatibility

Release note

Please refer to Release Notes Language Style Guide to write a quality release note.

None

[tiprow]

Hi @windtalker. Thanks for your PR.

PRs from untrusted users cannot be marked as trusted with /ok-to-test in this repo meaning untrusted PR authors can never trigger tests themselves. Collaborators can still trigger tests on the PR using /test all.

I understand the commands that are listed here.

Details

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.

[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2025-12-25 03:03:39.925408654 +0000 UTC m=+2306164.739186236: ☑️ agreed by XuHuaiyu.
• 2025-12-25 03:05:44.230530653 +0000 UTC m=+2306289.044308215: ☑️ agreed by qw4990.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 68.6241%. Comparing base (7dea15e) to head (2f20acf).
⚠️ Report is 18 commits behind head on master.

Additional details and impacted files

@@               Coverage Diff                @@
##             master     #65244        +/-   ##
================================================
- Coverage   70.7643%   68.6241%   -2.1402%     
================================================
  Files          1901       1880        -21     
  Lines        518640     512244      -6396     
================================================
- Hits         367012     351523     -15489     
- Misses       127111     138363     +11252     
+ Partials      24517      22358      -2159     

Flag	Coverage Δ
integration	41.6191% <100.0000%> (-6.5477%)	⬇️
unit	65.9392% <100.0000%> (+0.3954%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Components	Coverage Δ
dumpling	52.8700% <ø> (ø)
parser	∅ <ø> (∅)
br	38.4976% <ø> (-19.7370%)	⬇️

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: hawkingrei, qw4990, XuHuaiyu

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Details

Needs approval from an approver in each of these files:

• pkg/expression/OWNERS [XuHuaiyu]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[hawkingrei]

/retest

[hawkingrei]

/retest

[hawkingrei]

/ok-to-test

[windtalker]

/test unit-test

[windtalker]

/test pull-unit-test-next-gen

[tiprow]

@windtalker: The specified target(s) for /test were not found.
The following commands are available to trigger required jobs:

• /test fast_test_tiprow
• /test tidb_parser_test

Use /test all to run all jobs.

Details

In response to this:

/test unit-test

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.

[tiprow]

@windtalker: The specified target(s) for /test were not found.
The following commands are available to trigger required jobs:

• /test fast_test_tiprow
• /test tidb_parser_test

Use /test all to run all jobs.

Details

In response to this:

/test pull-unit-test-next-gen

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.

[windtalker]

/test pull-integration-e2e-test

[tiprow]

@windtalker: The specified target(s) for /test were not found.
The following commands are available to trigger required jobs:

• /test fast_test_tiprow
• /test tidb_parser_test

Use /test all to run all jobs.

Details

In response to this:

/test pull-integration-e2e-test

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.

[lance6716]

/retest

[tiprow]

@windtalker: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
fast_test_tiprow	2f20acf	link	true	/test fast_test_tiprow

Full PR test history. Your PR dashboard.

Details

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository. I understand the commands that are listed here.

[windtalker]

/retest-required

[windtalker]

/test mysql-test

[tiprow]

@windtalker: The specified target(s) for /test were not found.
The following commands are available to trigger required jobs:

• /test fast_test_tiprow
• /test tidb_parser_test

Use /test all to run all jobs.

Details

In response to this:

/test mysql-test

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.